Disable wayland support in the snap

[maxiberta]

Installed plasma-workspace-wayland, now the barrier snap crashes on start on X11 (!) with:

This application failed to start because it could not find or load the Qt platform plugin "wayland-egl"
in "".

Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, xcb.

Reinstalling the application may fix this problem.

Reproduced on Ubuntu 18.04 and Ubuntu 20.04.

This just completely disables any native wayland support and allows the app to start on X11. Afaik, this is a known issue with snaps, and this is the "common" workaround.

I think enabling proper wayland support should start by adding qtwayland5 to stage-packages.

Additionally, make sure the minimum basic tools for building are installed (not an issue in Launchpad build farm, but helps on any desktop pc with no g++).

[p12tic]

LGTM.

[p12tic]

@AdrianKoshka: I think you can merge this one.